Conventional electronic video and other gaming devices generate sounds such as music, sound effects noises and the like in response to sound-representing digital data stored in a memory device. However, in the past the sound signals so generated were monaural rather than stereophonic for a variety of reasons.
As is well known, "stereophonic" sound generally provides two independent (but related) audio channels (e.g., "left" channel and "right" channel). Each of the audio channels includes independent audio (and other) signal processing circuitry. The signals generated by the independent stereo audio channels are typically reproduced by spatially separated audio transducers (e.g., "left" and "right" loudspeakers or headset transducers).
In the sound recording industry, the different stereo channels are typically recorded and/or mixed independently such that the audio signals existing in the two channels upon playback are different but related. Due to the phase and other signal relationships between related sounds generated simultaneously (or nearly simultaneously) in the different channels, the listener perceives a two-dimensional spatial quality to the sound. Stereophonic sound thus provides a more enjoyable listening experience because the listener perceives he is immersed in an envelope of sound emanating from plural spatially-separated sources. This effect is especially enhanced when listening to the stereophonic sound through a stereophonic headset.
As is well known, it is possible using conventional computer techniques to synthesize stereophonic sound by providing left and right channel sound generators controlled by left sound data and right sound data, respectively, stored in a digital memory device. Unfortunately, twice as much memory is typically required for producing such stereophonic sound as compared to the case in which only monaural sound is being generated. Moreover, it is also necessary to provide separate sound synthesizing circuits ("sound sources") for the left channel and the right channel, increasing the complexity and cost of the resulting circuit configuration.
A pseudo-stereo sound generating apparatus is disclosed in laid-open Japanese Utility Model Application No. 66800/1983. This reference discloses receiving an AM broadcast signal with an AM broadcast receiver (tuner) and enhancing the received AM signal (which is monaural) to provide a pseudo-stereophonic sound effect. This document does not address the problem of providing stereophonic sound in a video gaming device having limited memory resources.
The present invention provides a pseudo-stereophonic sound generating apparatus and method which generates pseudo-stereo sound using inexpensive, relatively uncomplicated circuitry which actually reduces memory requirements.
The present invention also provides a novel memory cartridge which can be used in a video gaming device having pseudo-stereo sound generating circuitry.
The present invention further provides a novel hand-held video gaming apparatus including a pseudo-stereo sound generator.
A further important and advantageous feature provided by the present invention is a hand-held video gaming device in which sound effects can be generated stereophonically through a stereo headset.
In accordance with one aspect of the present invention, a plurality of independent sound synthesizer circuits are provided. Some of the sound synthesizer circuits may be used for generating left-channel output signals, others of the sound synthesizer circuits may be used for generating right-channel output signals, and still others of the sound synthesizer circuits may be used for generating audio signals for application to both the left and the right audio output channels. However, in the preferred embodiment of the present invention there is no permanent assignment of sound synthesizer circuits to audio output channels. Instead, audio switching circuits provided at the output of the sound synthesizer circuits selectively direct the various synthesizer circuit outputs to the left or right audio output channels as desired. The states of the analog switching circuits may be altered under program control to change the audio output channel the signal produced by a particular sound synthesizer circuit is directed to.
For example, in accordance with a feature provided by the present invention, a left channel audio signal bus and a right channel audio signal bus are provided. The left channel audio signal bus provides left channel audio signals to a left channel audio signal amplifier and associated sound transducer (e.g., the left channel transducer of a stereophonic headset). Similarly, the right channel audio signal bus applies a right channel audio signal to a right channel audio amplifier and associated sound transducer (e.g., a right channel transducer of the same stereophonic headset). A plurality of sound synthesizer circuits ("sound sources") are also provided. The sound sources in the preferred embodiment independently produce various audio signals (e.g., musical pitches, sound effects, etc.) under program control. The output of each (any) of the plurality of sound sources may be coupled to the left channel audio signal bus via left channel analog switches and/or to the right channel audio signal bus via right channel analog switches. The states of the analog switches are controlled by program control instructions and thus may be dynamically changed as desired.
Thus, the output of a particular sound source may be applied to only the left channel audio signal bus, to only the right channel audio signal bus, or to both the left and the right audio signal buses by simply selecting the states of the analog switches coupled to its output (and these states can be changed as desired under program control). By simultaneously or selectively turning on or off the left channel and right channel analog switches associated with a particular sound source, sound signals may be directed to one, the other or both audio output channels.
Since in accordance with the present invention it is possible to select the channel a particular sound source applies its output to, there is no requirement to store completely different sets of sound generating data (left channel and right channel) corresponding to the two sterephonic musical programs. That is, it is only necessary to store different sound generating data for controlling the plural sound generating sources which are to be active during a particular time. The additional data used for selecting which of the audio channels the various sound sources are to apply their outputs to requires very little additional storage space--allowing pseudo-stereophonic sound to be provided with only a slight addition in memory storage capacity. Since it is possible to select which channels a particular sound source signal is to be applied to, memory requirements do not increase substantially (in contrast with a situation in which left and right channel signals are stored separately in memory, which generally requires two times the amount of memory needed to store audio information for a monaural channel). Moreover, a more versatile and less complex circuit configuration is provided by the present invention, making it especially suited for generating sound effects within a miniaturized portable video gaming device.
In the video gaming device described above, a sound source signal generated by the sound source signal generating means is thus selectively outputted by the first and second (e.g., left and right) sound signal channels to a switching operation performed by the analog switching means so as to produce a pseudo-stereophonic sound.
The present invention also provides a memory cartridge detachably engageable to a video gaming device which provides stereophonic sound control signals. The video gaming device includes sound source signal generating means for generating a sound signal in accordance with data provided by the memory cartridge. Switching means may connect an output of the sound signal generating means to either or both of first and second sound output channels, and selectively applies the output of the sound source signal generating means to the first and/or the second sound signal output channels. For music generation, the memory cartridge preferably stores data representing the duration (length in time) of a musical note or rest; data associated with musical pitch; and "direction data" specifying the audio output channel to which the sound generated at the specified pitch and for the specified duration is to be directed.
The memory cartridge stores a sequence of such sets of data corresponding to a sequence of musical or sound effect events (i.e., notes and rests) and, in the preferred embodiment, accesses the data sets in the order of the sequence (with time separating the access of different data sets in the sequence) so as to specify the sequence of musical or sound effect events. In the preferred embodiment the memory cartridge may store plural data sets corresponding to a given instant in the sequence of musical or sound effect events--thus providing simultaneous control over multiple sound sources.
The memory cartridge in the preferred embodiment further stores program control instructions for reading respective data representing sounds for predetermined timings--thus providing a mechanism for applying the length (duration) associative data, musical pitch associative data and left/right channel specifier ("direction") data to the video gaming device in accordance with program control instructions read from the cartridge.
The memory cartridge of the preferred embodiment of the present invention preferably stores multiple data structures representing different aspects of the sound to be generated. In particular, the cartridge preferably stores a musical score data table representing information typically represented by sheet music (e.g., the pitch and duration of musical notes, and the duration of rests for a sequence of such notes and rests). This musical score data table in turn preferably provides offset addresses into a duration data structure mapping different musical note and rest durations stored in the musical score table into appropriate sound generator circuit timing control signals; and into a frequency data structure mapping different pitches into appropriate sound generator circuit pitch control signals.
In accordance with the progress of the computer program stored within the memory cartridge, the duration associative data, musical pitch interval associative data and left/right channel direction specifying data are read from the musical score table at predetermined timings (these timings are otherwise determined by program flow). Musical pitch of generated sounds is determined in accordance with musical pitch associative data and a sustained time period (i.e., length or duration) of that musical pitch is determined in accordance with the length (duration) associative data. The output multiplexing (switching) operation as described above is performed in accordance with the left/right channel direction specifying data to obtain right channel sound output or left channel sound output as desired. Thus, the sequence of musical notes stored in the musical score table can be generated in pseudo-stereophonic sound. Since the left or right channel data is stored in the memory cartridge and the left/right channel selection data specifies which channel the audio represented by any specific pitch and duration data is to be directed to, it becomes possible to easily generate or produce pseudo-stereo sound such as music or sound effects.
In accordance with a further feature of the present invention, a stereo/monaural changing circuit is connected to a stereo sound source from which left and right sound signals are independently outputted. The stereo/monaural changing circuit preferably includes an earphone jack for receiving a conventional stereo type audio plug. The earphone jack includes at least one switching contact as well as left and right channel audio contacts. The left channel audio contact conducts left channel audio signals to the headset left channel audio transducer, and the right channel audio contact similarly conducts right channel audio signals to the headset right channel audio transducer. In addition, a monaural audio transducer (e.g., a loudspeaker internal to the video gaming device) may be provided.
When no earphone plug is inserted into the earphone jack, the switching contact generates a control signal which automatically deactivates the independent left and right channel audio signal paths connected to the earphone jack left and right channel outputs, and automatically activates a combining ("mixing") circuit which combines the left and right channel audio signals together into a monaural signal. The combining circuit applies the combined audio monaural signal to the video gaming device internal loudspeaker. On the other hand, inserting an earphone plug into the earphone jack changes the state of the control signal produced by the earphone jack switching contact to deactivate the combining circuit (and thereby automatically deactivate the internal loudspeaker) and to instead complete the independent left and right signal channel paths to the earphone jack left and right channel contacts.
Thus, when the earphone plug is not inserted into the earphone jack, a monaural synthesized sound signal is provided to the internal speaker. When the earphone plug is inserted into the earphone jack, on the other hand, the left channel and right channel signal paths are not disabled and are instead respectively outputted to the left channel and right channel contacts of the earphone jack--and stereophonic sound is thus outputted to the stereophonic headset plugged into the earphone jack. In this way, the user may easily play the video gaming device as a completely self-contained unit and listen to monaural sound generated by an internal loudspeaker. If on the other hand, the player would like to experience the sound enhancement provided by the pseudo-stereo sound generating capabilities described above, he need only insert the plug of stereo headset into the earphone jack and place the headset on his head.
Thus, this feature of the present invention provides a novel stereo/monaural changing circuit capable of selecting between stereophonic sound and monaural sound even though the sound generating data stored in the data cartridge controls the sound generating circuitry to generate pseudo-stereophonic sound. Such a stereophonic/monaural selecting circuit is very effective for generating sound effects in a hand-held video type gaming machine.